They are not in danger, says Volodymyr Yegerov, a nuclear safety expert with Ukraine’s National Academy of Sciences, who also acted as VOA’s guide on a tour of the site.

“If you comply with the rules of radiation safety, it is absolutely safe,” he said. “The dose of radiation one gets here is a little bit higher than in Kyiv, for instance.”

Human error and poor reactor design have been blamed for the accident in what was then the Soviet Union. During a shutdown test in the early hours of April 26, 1986, a steam explosion blew the roof off reactor 4. Blocks of super-heated graphite rained down on the site and huge amounts of radioactive particles were released into the air.

Then, as now, the firefighters and so-called "liquidators" who first tackled the blaze are lauded as heroes. At least 28 of them died from acute radiation sickness.

Archbishop Theodore Bubnyuk of the Ukrainian Orthodox Church conducted a religious ceremony this week to honor the victims.

“It is undoubtedly a great tragedy, by which many individuals were affected,” he told VOA. “We are still losing many people because of it. It is a great pain, a massive wound for our country and our nation.”

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The 30th anniversary is significant as the so-called concrete "sarcophagus" that was hastily built over the reactor has a three-decade life span.

A giant arch is designed to replace it and is nearing completion. Officially called the "New Safe Confinement," it has taken six years and around $2 billion to build. Sometime in 2017, the structure -- which is tall enough to contain the cathedrals of St. Paul in London or Notre Dame in Paris -- will be moved on rails over the reactor.

“It will not only serve as a shield from radiation, but will also allow dismantling of the old radioactive structures. First of all, the old concrete sarcophagus, which is not in good condition. As a result of these works, in 100 years there is to be a green lawn here,” said Yegerov.

A monument at the Chernobyl Fire Station to 32 of its crew who died responding to the explosion at the #4 reactor, March 20, 2014. (S. Herman/VOA)

It is an optimistic vision, but the area won’t be habitable for tens of thousands of years.

The 2,600 square-kilometer exclusion zone is an under-used resource, said environmental consultant Roman Zinchenko, who has visions of turning the area into a vast green energy site.

“This is the site where both we humans, and nature, heal the wounds. And the revival of this place can be a very important lesson for not just Ukraine, but all humanity.”

Since 2011, tourists have been allowed to visit Chernobyl. Among the most popular sites is the so-called "Russian Woodpecker," a vast radar system designed to protect then-Soviet-controlled Kyiv from attack.

Much of the Chernobyl exclusion zone provides a snapshot of Cold War tensions, frozen in time in 1986.

The world has changed much in the intervening three decades. Some argue it is time to seek a new future for Chernobyl.